The present invention relates to hydrocarbon fluids and their uses. Hydrocarbon fluids find widespread use as solvents such as in adhesives, cleaning fluids, solvents for decorative coatings and printing inks, light oils for use in applications such as metalworking and drilling fluids. The hydrocarbon fluids can also be used as extender oils in systems such as silicone sealants and as viscosity depressants in plasticised polyvinyl chloride formulations. Hydrocarbon fluids may also be used as solvents in a wide variety of other applications such as chemical reactions.
The chemical nature and composition of hydrocarbon fluids varies considerably according to the use to which the fluid is to be put. Important properties of hydrocarbon fluids are the distillation range generally determined by ASTM D-86 or the ASTM D-1160 vacuum distillation technique for heavier materials, flash point, density, Aniline Point as determined by ASTM D-611, aromatic content, viscosity, colour and refractive index. Fluids are can be classified as paraffinic such as the Norpar® materials marketed by ExxonMobil chemical Company, isoparaffinic such as the Isopar® materials marketed by ExxonMobil Chemical Company; dearomatised fluids such as the Exxsol® materials, marketed by ExxonMobil Chemical Company; naphthenic materials such as the Nappar® materials marketed by ExxonMobil Chemical Company; non-dearomatised materials such as the Varsol® materials marketed by ExxonMobil Chemical Company and the aromatic fluids such as the Solvesso® products marketed by ExxonMobil Chemical Company.
Unlike fuels fluids tend to have narrow boiling point ranges as indicated by a narrow range between Initial Boiling Point (IBP) and Final Boiling Point (FBP) according to ASTM D-86. The Initial Boiling Point and the Final Boiling Point will be chosen according to the use to which the fluid is to be put however, the use of the narrow cuts provides the benefit of a precise flash point which is important for safety reasons. The narrow cut also brings important fluid properties such as a better defined viscosity, improved viscosity stability and defined evaporation conditions for systems where drying is important, better defined surface tension, aniline point or solvency power.
These hydrocarbon fluids are derived from the refining of refinery streams in which the fluid having the desired properties is obtained by subjecting the most appropriate feed stream to fractionation and purification. The purification typically consists of hydrodesulphurisation and/or hydrogenation to reduce the sulphur content or, in some instances, eliminate the presence of sulphur and to reduce or eliminate aromatics and unsaturates. Traditionally the aliphatic hydrocarbon fluids are produced from virgin or hydro-skimmed refinery petroleum cuts which are deeply hydrodesulphurised and fractionated. If a dearomatised fluid is required the product that has been deeply hydrodesulphurised and fractionated may be hydrogenated to saturate any aromatics that are present. Hydrogenation can also occur prior to the final fractionation.
There is currently a trend towards the use of fluids with extremely low levels of aromatics, extremely low sulphur levels and with higher initial boiling points. These requirements are driven by environmental and/or safety considerations and/or specific end-uses. The existing processes in which a light gas oil or virgin gas oil is first hydrofined and, if required, hydrogenated are constrained to feeds with a maximum ASTM D-86 Final Boiling Point (FBP) of 320° C. Feeds with higher boiling points, which tend to have higher sulphur levels can render the life of the hydrogenation catalyst too short and the higher content of aromatics in these feeds also limits the material that can be hydrogenated in an economic manner. Generally the boiling range of hydrocarbon fluids is measured using the atmospheric boiling measurement technique ASTM D-86 or its equivalent. However, ASTM D-86 is typically used to measure boiling temperature up to around 370° C., more typically up to 360° C. If however the fluid contains a fraction boiling above 365° C. it may be more convenient to use the ASTM D-1160 technique which measures the distillation temperature using vacuum techniques. Although the fluids specifically discussed herein are stated to have ASTM D-86 boiling points the boiling range of a fluid having a final boiling point above 365° C. may be measured by ASTM D-1160.
Further requirements for hydrocarbon fluids are that they have good cold flow properties so that their freezing points are as low as possible. There is also a need for improved solvency power particularly when the fluids are used as solvents for printing inks where it is necessary that they readily dissolve the resins used in the ink formulations.